This is a flight backup film magazine for the H-alpha #1 pointing telescope of the planned second Apollo Telescope Mount. This telescope imaged the sun in filtered light, admitting only the red hydrogen alpha line. The instrument was used by the astronauts to locate interesting areas of solar activity and to boresight other spectrographic instruments.
NASA transferred the magazine to NASM in 1982.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.